Hello all. I know this is only my first post, but the truth is I've been an S10 Blazer owner for several years, and a lighting enthusiast for several years as well. I did put on the Envoy front end onto my 96 Blazer a couple years ago, and in doing so, I installed the OEM xenon headlight fixtures which I had purchased on eBay around that time. I had bought those fixtures WITHOUT any bulbs in them, so I made my own mounting retainer plates (see pics):

So I installed the standard D2S bulb in (looks like a direct interchange, right?)

...where the guy in there brings to my attention why my beam pattern has likely been so HORRID for the last 2 years. It looks as though the specialty Envoy HID bulb is a special bulb possibly unlike any other. This guy claims that the true Envoy Philips #16526491 (or #16526104) bulb may have a capsule that sits in a little deeper into the fixture than the D2S capsule allows. If this is true, then this would explain why the beam is not very uniform on my headlights. Because the bulb's capsule is not centered in the focal point of the fixture's reflector.

HERE'S MY QUESTION / FAVOR TO ASK of a qualifying person here:

I would like to find somebody who has either, a burned out OEM Envoy bulb they could either measure for me or sell to me. Or if somebody wouldn't mind taking out their OEM Envoy HID bulb and measuring it for me, and snap some pictures of it as well. I would be willing to PAY for this info. I could send money via PayPal or something. I just need somebody who has one of these original equipment bulbs to measure the distance from the seat of the flange on the bulb (where it seats against the fixture bulb mount), measure from that seat out to the center of the capsule, and provide that dimension to me. Then if it IS such that the D2S bulb's capsule does not sit in as deep as the OEM bulb, then I will proceed to modify my seat to allow my D2S bulb to sit in the correct position based on that measurement. And I will come back here and post all of my results and pictures of the before and after beam patterns for all to see. I have a sneaking suspicion that this is the cause for my poor spotty beam pattern that seems to have and empty spot in the middle of the 2 hotspots.
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OK, so I wasn't going to hold my breathe waiting for a response here since I was serious about solving this dilemma pretty quickly, and I DID solve it. Last night, finally... Hopefully, this will help others

The 98-00 ENVOY OEM bulb is NOT a D2R nor a D2S as some have suggested before. I went on ahead and purchased a USED original equipment Envoy bulb on eBay the other day just to see it in person, and to make some precise measurements and a formal comparison.

Please see my 18 captioned pictures here: http://www.ojbox.com/blazer/ENVYvsD2S.htm ...which thoroughly show the details of this problem and how I fixed it on my Blazer with Envoy light fixtures. These pictures I took are not perfect, but they do get the point across.

Turns out that the Envoy bulb has the EXACT same distance from the flange/bulb-seat to capsule/filament as the 9006 bulb. This might make sense as the original non-xenon GMC and Chevy trucks of the same year range all used 9006/9005, and maybe some goofball at GM thought they should all be the same, or that this was the 'ideal' focal point in a perfect world or something like that. But really, my simple logic is just telling me that they just wanted to build a proprietary bulb so that they could charge an arm and a leg for the replacements. Car companies can't get away with this type of behavior as much anymore though, since many Americans are loosing their loyalty with the whole 'Made In the USA' slogan and putting their money towards foreign made cars where those manufacturers don't pull these selfish stunts to such extremes (I mean $500 for a light bulb is a bit ridiculous).

So in my case, I opted to modify the light fixture to be able to correctly house an unmodified D2S bulb. But the other option is that you can get a 9006 HID re-based bulb (verifying the re-based distance is correct before actual install), and you must also modify the mounting tabs of the 9006 bulb base enough to make it fit into the factory Envoy fixture and then build a retainer (kinda like I did for mine in the pictures) to hold the bulbs perfectly in the center of the bulb socket, and firmly into position. I do have a set of 9006 rebased HID bulbs here (see the pictures in the above link) which DO have the correct focal point as a normal 9006 bulb (I know, since I rebased the original rebase job since the original rebase job from the original bulb peddler was crap, but my re-base job I did on it was perfect). But the main problem was, that these 9006 capsules I got are not even true Philips or Osram and the support braces for the capsules are not even very heavy duty (very light weight) and you can flex them to some degree and the bulb just doesn't feel very secure), so I opted NOT, to use those for this. And since I do have plenty of Philips 85122 OEM D2S capsules laying around, it made more sense to me, to mod the fixture to just take a D2S out of the box. But the easier option for many who lack the tools to effectively mod the fixture and get the dimensions just right, then I would recommend installing 9006 re-bases and just Dremmel the mounting tabs just enough so that they will drop into the Envoy sockets, and the 9006 depth will be the same as the Envoy HID bulb. If you choose to use the unmodified D2S bulb, then you need to do something to make it sit 5/32" (of an inch) deeper into the fixture. This is the magic number that I paid $200 to be able to measure.

Does anybody want to buy this OEM Envoy bulb/igniter, (complete with ballast-to-igniter harness wire) from me now? I will probably just put it back up on eBay now at this point unless someone here wants it, then maybe we can make a deal.

I bought a 2000 Envoy last summer. When I read in the manual that it had HID, I was pretty impressed. When one headlight went out, and I removed both headlight assemblies to small plastic clips loosely holding a 9006 bulb in the factory assembly, I was no longer impressed.

The factory bulbs/ballast are gone, as is any of the mounting hardware that would have held the bulb in. I would like to install HID headlamps, and probably get a 3500k kit for the fog lamp assembly as well.

Starting from this point, what would recommend I do? Buy a 9006 Based aftermarket HID bulb and come up with someway to mount it in there? I'd prefer to avoid modifying the housing due to it's rarity (in case I break it), but between my friends and I, I should be able to get a mounting system fabricated. Is there another bulb type that might work like a D1S??

I finally got around to installing my lights last month. Which I've had sitting in my garage since last year. I also noticed that split beam as well, but could not put my finger in the issue. Everything you said makes since. I went ahead and did the retro with 9006 bulb. I too would like do the same setup you did. Great info. Good write up.

We recently bought a 2000 Envoy with one low-beam out, not knowing the implications. After bringing it home, reading the manual, and finding the disconnected ballast assembly hiding in the rear storage compartment, I knew we had a potentially spendy problem.
I did some research online and found another Envoy owner who simply swapped his envoy headlight assemblies for Jimmy headlight assemblies. He recommended a company on Amazon that sells assemblies, new, complete with low and high beam bulbs for $35/each. The battery-side connector into the ballast is a 9006 2-pin connector. All I had to do was pull the connector off the ballast, cut the headlight off the other side (because getting to the ballast to remove it is a massive PIA), and replace the assemblies. Sure, they're not HID and they're not the Envoy stock headlights, but they fit, work, and are easy to replace bulbs in when necessary. It would also be easy now, to put after-market HID bulbs in if you wanted to.